1. Field
Aspects of embodiments according to the present invention relate to an organic light-emitting display device.
2. Description of Related Art
Organic light-emitting display devices (OLEDs) have been applied in electronic/electric products such as digital cameras, video cameras, camcorders, personal digital assistants (PDAs), smart phones, ultra-thin televisions, ultra-slim laptop computers, tablet personal computers, and flexible display devices.
Organic light-emitting display devices display images in color when holes and electrons, injected respectively from an anode and a cathode, recombine in an organic emission layer. An organic light-emitting display device has a stacked structure including an anode, a cathode, and an organic emission layer interposed between the anode and the cathode.
However, it is difficult to achieve high light-emission efficiency with such a structure, and thus additional intermediate layers, including an electron injection layer, an electron transport layer, a hole transport layer, a hole injection layer, etc., are optionally interposed between the organic emission layer and each of the electrodes.
Here, organic light-emitting display devices may be classified into passive matrix (PM) OLEDs and active matrix (AM) OLEDs according to a driving method. An AM OLED includes a thin film transistor (TFT) functioning as a switch. It is desirable to improve reliability and reduce leakage current property of polysilicon TFTs in an off state.
In order to improve reliability and reduce leakage current property of the TFTs, a lightly doped drain (LDD) structure has been used.
In a TFT having the LDD structure, a gate electrode is formed, and then low dose impurities are doped for forming the LDD structure. Then, high dose impurities are further doped by a photolithography process for forming a source region and a drain region of the TFT.
However, a TFT having the LDD structure has a reduced driving current and is made using more masks. Thus, yield is reduced and manufacturing costs are increased.